The present invention concerns diorganopolysiloxane compositions with excellent heat resistance, especially diorganopolysiloxane compositions suitable as oils for synthetic fibers.
Natural fibers such as cotton, and wool have excellent smoothness, because of the wax or lanolin adhered on their surface. However, such smoothness is lacking in synthetic fibers such as nylon fibers, polyester fibers, polypropylene fibers, and TEFLON. Thus, oils are used on raw synthetic fibers to provide smoothness and antistatic properties. The yarns prepared from such raw fibers are subjected to false twisting for various purposes such as bulk, and stretch recovery. At this time, the yarn is brought into contact with a hotplate at a temperature of 300.degree. C. or more, and such yarns are treated with false twisting oils to impart heat resistance to them.
In the preparation of carbon fibers and graphite fibers from polyacrylonitrile synthetic fibers, the precursor obtained by spinning is heated at 300.degree.-400.degree. C. to obtain flame-resistant fibers, and an oil is used to prevent the filaments from sticking together.
Compared with raw fibers for apparel, the raw fibers for industrial tire cords are brought into contact with hot rolls for a long time and heat-set at 300.degree.-350.degree. C. Thus, such raw fibers are treated for enhanced heat resistance with lubricants for raw fibers for tire cords.
Mineral oils and animal and vegetable oils are used in such lubricants for raw fibers and false-twist yarns. As lubricants for the raw fibers for carbon fibers, e.g., dimethylsilicone oil (see Japanese Kokoku Patent No. Sho 51[1976]-12739) and amino-group-containing silicone oils (see Japanese Kokai Patent Application Nos. Sho 60[1985]-185879, Sho 60[1985]-185880) have been proposed.
However, the mineral oils and vegetable oils have low heat resistance, and they tend to decompose at low temperatures, causing problems in bringing out their functions under high temperature. The silicone oils described above do not have sufficient heat resistance; thus, when exposed to high temperature for a long period of time, they become a tacky gel, which accumulates, causing reduced heat treatment efficiency and reduced fiber running, fiber disturbances and breakage. Thus, improvements are desired in synthetic fiber lubricants used for raw fibers, false-twist fibers, raw fibers for carbon fibers, and raw fibers for tire cords.